As one of focus detection methods of an imaging lens, Patent Literature 1 discloses an apparatus of performing focus detection by a pupil division method using a two-dimensional sensor where a micro lens is formed in each pixel of the sensor. In the apparatus disclosed in Patent Literature 1, a photoelectric converter of each pixel which constitutes the sensor is divided into a plurality of photoelectric converters. The divided photoelectric converters are configured so as to receive light in regions having pupils of an imaging lens different from each other via a micro lens.
Patent Literature 2 discloses an image pickup device which performs a pupil division by displacing a sensitivity center of a light receiving unit with respect to an optical axis of an on-chip micro lens in a light receiving element (pixel) of a part of an image pickup element. These pixels are arranged between imaging pixel groups at a predetermined interval as focus detection pixels so that phase difference focus detection is performed. Since the region where the focus detection pixel is arranged corresponds to a defect of the imaging pixel, image information is created by performing an interpolation of the information using peripheral imaging pixel information.
Patent Literature 3 discloses a focus detection device which performs a pupil division of two divisions of a light receiving unit of pixels of a part of an image pickup element. The focus detection device performs phase difference focus detection by independently processing outputs of the light receiving unit for which two divisions have been performed and also adds the outputs of the two-divided light receiving unit to use it as an imaging signal.
Patent Literature 4 discloses a method of performing focus detection by performing a correlation calculation of an image generated from light beams transmitted through different pupil regions of an imaging lens.